Urology Flashcards
What is the mean age of diagnosis for prostate cancer?
70-79, increasing with age
Which lower urinary tract symptoms are considered irritative and which obstructive?
Irritative- due to storage of urine
Urgency, incontinence, frequency, nocturia
Obstructive- voiding issues
Hesitancy, poor flow, intermittent stream, terminal dribbling, incomplete emptying
How would prostate cancer be investigated?
Digital rectal exam
Age-related prostate-specific antigen levels
Free: total PSA levels
(the amount of free floating PSA compared to protein-bound PSA reduces in prostate cancer)
Transrectal ultrasonography with guided biopsy.
CT/MRI + isotope bone scan if PSA >10ng/ml
How is prostate cancer graded and staged?
Which system is most useful for prognosis?
GRADING- Gleason score- x+y
Looks at architectural pattern rather than cytology.
Looks at the organisation of the glands to determine how differentiated cells are- are glands recognisable
x = the most frequent pattern seen (more than 50% of the tumour)
y = the next most frequent pattern seen in sample
STAGING TNM score will be given
T= tumour size, related to it’s infiltration of the lobes or the prostate capsule etc
N= nodes, M= metastases
Gleason grade is more useful for estimation of prognosis, but PSA TNM and Gleason will be considered when classifying risk as low, medium or high.
When would active surveillance be suitable in prostate cancer?
For patients with low risk:
low PSA (below 10ng/ml)
stage T1/T2- tumour extends throughout prostate lobes but not the capsule
Low gleason score (6)
NB: PSA is a serine protease used to liquify seminal fluid
What are the potential side effects of radical prostatectomy + external beam radiotherapy used in prostate cancer?
impotence and incontinence
aka
erectile + bowel dysfunction
When would active surveillance, prostatectomy, external beam radiotherapy, hormones or brachytherapy be used in prostate cancer?
Active surveillance- low risk disease or reduced life expectancy due to comorbidity
Prostatectomy- localised disease
Radiotherapy- localised or localised advanced disease.
Brachytherapy (radioactive seeds)- less incontinence than other Rx, but if significant obstructive/irritative symptoms they may worsen.
Makes resection more difficult afterwards.
Hormone treatment- when life expectancy is below 10 years or metastatic disease.
70 year old man with prostate cancer taking LHRH agonist (Goserelin) has had numbness in his legs and has fallen twice.
What question to ask and what management?
Spinal cord compression from bony metastases.
LHRH used to inhibit LH release, may cause initial peak in testosterone, which is converted to oestrogen and increases bone growth.
‘Has there been any urinary incontinance?’
Rx: High dose prednisolone, MRI spine, radiotherapy, start hormone therapy.
What type of cancer is prostate cancer and where does it arise in the prostate?
95% adenocarcinoma- as tissue is glandular
5% sarcoma- from stroma of prostate
70% arise in the peripheral zone, many multifocal
In hormonal treatment of prostate cancer, LHRH agonists are given. How can an initial surge in testosterone be prevented?
Anti-androgen cover for the first 2 weeks may be offered using:
Biclutamide (androgen receptor antagonist)
Flutamide
Cyproterone acetate
What are the risk factors for bladder cancer?
Find 5.
- Commoner in men than women (2:1)
- SMOKING!!!!! -aromatic amines (2-6x increased risk)
3. Jobs: Textiles Rubber industries- analine dye Gas works Sewage treatment
- Chronic irritation:
Long term catheter
Stones
Schistosomiasis (haematobium) via squamous cell cancer. - Previous radiation exposure
Pathology of bladder cancer- types
90% transitional cell carcinoma
squamous cell carcinoma- if chronic irritation from catheters, stones or schistosomiasis
adenocarcinomas- from urachal remnants of the bladder.
(urachus is the fibrous remnant of the allantois- which drains the fetal baldder)
phaeochromatomas rarely.
Patient with frank haematuria or persistent haematuria after UTI is treated.
25% of macroscopic haematuria = cancer
Tends to be painless
Irritative symptoms of: frequency, nocturia, urgency and incontience may also present in bladder cancer.
How should suspected bladder cancer be investigated?
Cystoscopy
Transurethral resection of bladder tumour
include detrusor muscle to determine muscle invasion.
Urine cytology-prior to cystoscopy
Pelvic exam/bimanual under anaesthesia to see if pelvic mass is present- indicates T3 level of disease at least.
Intravenous Urogram
In superficial non-invasive bladder cancers (pTa and pT1) how can reoccurrence be prevented following resection?
pTa and pT1 mean no invasion into bladder muscle yet.
Mitomycin C made be given into the bladder within 6-24 hours, post-resection.
Mitomycin C= potent DNA crosslinker
In high grade non-invasive/superficial bladder cancer- pT1 G3:
intravesical BCG floods the bladder to stimulate the immune system.
Given weekly for 6 weeks.
Regular follow-up cystoscopies needed to monitor disease.
How should ‘carcinoma in situ’ of the bladder be treated?
Carcinoma in situ is where malignant cells that are highly dysplastic have not yet invaded the epithelium to enter muscle.
BCG may be given weekly for 6 months or radical cystectomy may be better (removal of the bladder).
How should muscle-invasive bladder cancer be treated?
Surgery
Men- cystoprostatectomy and pelvic node dissection
Women- pelvic exenteration
anterior pelvic clearance, hysterectomy, salpingo-oopherectomy and upper third vaginectomy
May reconstruct bladder- orthotopic neobladder may use small bowel as the reservoir then reconnect this to the urethra, like a normal bladder.
Ileal conduit takes a piece of small bowel (joining the bowel back up after piece removed) and connects ureters to it, this then connects to urostomy bag on skin.
Neoadjuvant or adjuvant chemotherapy afterwards.
What percentage of cancer in men is due to prostate?
What proportion of cancer mortality is due to prostate cancer?
Commonest cancer in men
1 in 10 men aged 70 get it.
13% of deaths from cancer in men are due to prostate cancer.
What type of bone lesions are seen if prostate cancer metastases to bone?
Osteoblastic thickening of the bone (sclerotic), resembling Paget’s disease.
Other cancer mets- breast/renal cancers form lytic thinning lesions.
How does the risk of prostate cancer increase with the number of first degree relatives who’ve had it?
One 1st degree relative = 2x
Two relatives = 5x
Three relatives =11x
How should locally advanced prostate cancer be treated?
How should metastatic prostate cancer be treated?
With hormone therapy and external beam radiotherapy.
Metastatic- LHRH analogues + anti-androgen cover (to obstruct adrenally produced androgens).
What is intermediate risk prostate cancer?
Gleason 7
PSA 10-20
T stage- 2b
means tumour is in more than half of one of the lobes.
(T3 is both lobes but within capsule)
What is Peyronie’s disease?
Localised connective tissue disorder
Fibrous inelastic scar following inflammation of tunica albuginea
inability to extend corpus cavernosum causes penile angulation
PC: pain, penile nodes, penile angulation, erectile dysfunction
What is phimosis?
At birth the foreskin is fused to the glans penis and is therefore not retractable.
How is Peyronie’s investigated?
Photos to measure deformity
Colour Doppler USS- to assess vascular or plaque abnormalities
Contrast MRI- if complex or extensive fibrosis
How is Peyronie’s disease managed In the acute phase?
Curvature:
Pentoxifylline
A PDE and TGF-1 inhibitor
Verapamil
(Ca2+ channel blocker with smooth muscle)
Pain- Colchine + Vit E
Colchine prevents neutrophil mobility (reduce inflammation)
What proportion of men have congenital curvature, what is it caused by?
4-10%
Asymmetric growth of the corpus cavernosum
Rx: Nesbit procedure (excise on opposite site to deformity)
16 dot plication (shortens the convex side using sutures)
During sex, there was a ‘popping’ noise and sudden loss of erection.
Now my penis is very bruised.
PENILE FRACTURE
rupture of corpus carvernosum ± spongiosum/urethra
IHx: surgical exploration- check for urethral injury
US to isolate defect
Rx: excavate haematoma, close tunica alburginea
How is male infertility investigated?
2 semen analyses (fresh)
look at sperm number, morphology, motility
Seminal vesicle function
FSH level
Genetic tests
DNA karyotype
CF gene
Y microdeletionsWhat investigations suggest ejaculatory duct obstruction?
Semen analysis: low volume, low pH, no fructose
Transrectal ultrasound scan after ejaculation- low sensitivity
Rx: surgery
What needs to be assessed in erectile dysfunction?
Vascular risk factors for atherosclerosis- diabetes, smoking, cholesterol, hypertension
Testosterone
IIEF-5 score is a questionnaire to find out severity of ED
Penile doppler USS- inject PGE1 to induce tumescence
Rigiscan- two rings measuring tumescence, number + duration of nocturnal erections. Demonstrates psychogenic ED.
How is organic erectile dysfunction managed?
PDE-5 inhibitors (prevent cGMP breakdown, more SM relaxation)
CI: nitrates
recent MI, stroke, hypotension, unstable angina
Intracavernosal injection
Given when oral treatments have failed, inject at right angles to corpus cavernosum on the lateral aspect of the penile shaft
Vacuum erection device
Penis is vacuum chamber to increase blood flow, constriction band maintains blood flow there.
Surgery- penile prosthesis (inflatable corpus cavernosum) or penile revascularisation- if clearly a vascular disorder
Has had an erection for last 4hours + without sexual stimulus
PRIAPRISM
What factors make a urethritis more likely to be sexually acquired and which suggest underlying UTI?
Sexually acquired:
New partner/risky sex in last 4 weeks
PC: dysuria, urinary frequency, urethral discharge
UTI:
Unchanging sexual relationships
Aged above 50
PC: frequency, loin pain, malaise, pyrexia
Testicular cancer risk factors
Undescended testes
Infertile men
Contralateral testicular tumour
Kleinfelters (XXY)
Tumour markers for testicular cancer?
AFP (yolk sac, embryonal, teratocarcinoma)
HCG (seminoma, choriocarcinoma, embryonal, teratocarcinoma)
lactate dehydrogenase
When should you refer haematuria?
If visible/frank haematuria
Symptomatic non-visible haematuria
40+ year old with non-visible haematuria
Persistent non-visible haematuria = 2/3 tests +ve
What causes transient (non-significant) haematuria?
UTI- check dipstick for leukocytes and nitrates
Exercise induced
Menstruation
What initial investigations would you do for
symptomatic non-visible haematuria
or persistent asymptomatic haematuria?
Exclude UTI or other causes- dipstick
Plasma creatinine/eGFR - glomerulonephritis
Measure proteinuria on random sample
Blood pressure- nephrotic syndrome
PLAIN KUB XRAY
ULTRASOUND RENAL TRACT
If haematuria is significant how do you decide between a urology or nephrology referral?
Nephrology if
eGFR below 60
proteinuria of PCR >50mg/mmol or ACR >30mg/mmol
everything else urology
for cystoscopy and imaging
What urological investigations used for significant haematuria?
(Visible, symptomatic non-visible or persistent non-visible)
Urine culture and cytology
Cystoscopy
Renal ultrasound
CT UROGRAM
Causes of haemospermia in under 40s
Inflammation of prostate, urethra, epididymus
Infection:
STDs- gonococcus
Entercoccal faecalis, chlamydia trachomatis, viral HSV
Tumour- rare
Causes of haemospermia in 40+ year olds?
Iatrogenic:
post-transrectal ultrasound
prostate biopsy
post prostate cancer radiotherapy etc
3.5 % Cancer: bladder prostate testicular benign prostatic hyperplasia seminal vesicle carcinoma- rare
Vascular:
dilated veins in prostatic urethra
hypertension
Haemospermia investigations?
If persistent or reoccurring:
FBC, PSA, LFTs, clotting
Transrectal USS
Flexible cystoscopy- look for polyps, urethritis, cysts, foreign bodies, stones, vascular abnormalities
Renal ultrasound
Pelvic MRI
Older man has some suprapubic pain, frequency + urgency.
Doctor does a dipstick and notices microscopic haematuria.
Likely diagnosis?
LUTS + peeing blood = bladder cancer
Carcinoma in situ of bladder presents this way and can be very aggressive.
Elderly man presents with a 4/12 history of wetting the bed.
On examination his abdomen looks distended.
Likely diagnosis?
High pressure chronic retention.
Distension due to grossly enlarged bladder, will be tense on palpation if high pressure.
May drain 2L off with catheterisation.
Patient presents with recent onset hesitancy, terminal dribbling, frequency and some loss of sensation to backs of his thighs.
What question needs to be asked?
What investigation is important?
Could be due to spinal cord compression, cauda equina syndrome or a sacral/pelvic tumour
Ask if can feel it when they wipe their bum (S3-5 dermatomes)
Ask about weight loss
MRI scan to determine neurological cause.
Causes of nocturia
Urological:
benign prostatic obstruction
overactive bladder
incomplete bladder emptying
Diabetes:
mellitus
insipidus (central)- lack of ADH
insipidus (nephrogenic)- ADH resistance
Renal failure Hypercalcaemic Obstructive sleep apnoea Autonomic failure Drugs- lithium causing ADH resistance Idiopathic
How should nocturia be investigated?
Record frequency and volume of each void over 24 hours for 7 days.
Definition of polyuria and causes
More than 3L of urine output per 24 hours
Solute diuresis- diabetes
Water diuresis- ADH resistance, or lithium therapy causing resistance
Definition of nocturnal polyuria
Production of more than 1/3rd of total urine output in 24 hours between midnight and 8pm.
Physiologically urine production normally reduces at night.
What is stress incontinence and what is it caused by?
Leakage of urine on coughing or sneezing or exertion.
Increase in abdominal pressure without detrusor contraction.
Caused by intrinsic sphincter deficiency, from bladder neck hypermobility ± neuro deficits
What is urge incontinence and what is it caused by?
Leakage of urine when urge to pee.
May be due to bladder overactivity or if bladder is irritated (infection, tumour, stone).
Patient has a hysterectomy and now complains of a constant leak of urine. What might be causing this?
Fistula communication between the bladder and vagina, post surgery.
If lifelong and low volume, can be due rarely to an ectopic ureter draining into the vagina instead of the bladder.
What is the nervous supply to the bladder?
Pelvic nerve = parasympathetic to detrusor muscle.
ACh- M3 receptors causes contraction and urination.
Hypogastric nerve = sympathetic to detrusor muscle.
NA-B3 receptors causes relaxation of detrusor muscle, no weeing.
What nervous supply controls the internal sphincter and external sphincters of the bladder?
Hypogastric nerve = sympathetic to internal sphincter
NA- a1 receptors cause contraction allowing wee storage.
Women don’t have an anatomical internal sphincter
Pudendal nerve = somatic to external sphincter
ACh- nAChR cause contraction ensuring closure for wee storage.
What comprises the internal sphincter of the bladder in men and women?
In women, it is functional not anatomic
= bladder neck and proximal urethra
In men it is anatomical
= bladder neck and prostate
What is the danger of chronic urinary retention in men?
How is it managed?
If the retention leads to a tense bladder, there may be back pressure onto the kidneys leading to renal failure in 30%.
Rx: intermittent self-catheterisation or indwelling catheter (if bed bound)
How can detrusor overactivity be investigated?
Urodynamic studies illustrate detrusor contractions during the filling phase of the bladder.
When spontaneous or provoked these contractions may cause urinary incontinence.
What can cause low bladder compliance and how might this provoke urinary incontinence?
Without a compliant bladder, filling may lead to a high level of pressure due to increased muscle tone or reduced bladder elasticity.
Myelodysplasia- associated with abnormal development of sacral structures
Spinal cord injury
Radical hysterectomy- scarring
Radiation/interstitial cystitis (scarring)
Proposed mechanisms of stress and urge incontience?
Urge
Detrusor overactivity
Low bladder compliance
Stress
Urethral hypermobility- weak pelvic floor allows descent of bladder neck with increased intra-abdominal pressure
Intrinsic sphincter deficiency
surgery, aging, menopause, childbirth, radiotherapy to prostate
Investigations for urinary incontinence?
Bladder diary- fluid intake, frequency, volume, incontience episodes, urgency, pad usage
Urinalysis + culture- UTI
Flow rate and post-void residual volume (uses USS)
Blood tests, ultrasound scans, cystoscopy
Urodynamic studies
What do urodynamic studies examine?
Pressure of stress incontinence.
Contractions during filling phase (detrusor overactivity)
Compliance (pressure change with volume)
Risk factors for stress incontinence?
Women:
Childbirth, obesity
Ageing, oestrogen withdrawal (menopause)
Previous pelvic surgery
Men:
Sphincter damage
Pelvic fracture or surgery
Prostatectomy or radiotherapy
1st line Rx for stress incontinence?
1st line: Pelvic floor muscle training- for 3 months
8 contractions 3 times a day
Lifestyle- weight loss, smoking, Rx constipation, modify fluid intake
What is the difference between the surgical approaches for stress incontinence?
Urethral bulking- increases outflow resistance
shouldn’t be given if urge incontinence coexists
Retropubic suspension- more invasive than suburethral sling. Elevates and fixes the bladder neck via the pelvic bones above pelvic floor
Suburethral slings or tapes- more superficial, can be inserted under local anaesthetic as day cases. Hooks around urethra lower down outflow tract.
Artificial urethral sphincter- uses a pump to release pressure. Used if other measures have failed or in severe incontinence
1st line Rx of urge incontinence?
Behaviour:
Bladder training- delay micturition, pelvic floor exercises for 6 months
Lifestyle:
Weight, fluid intake, avoid caffeine, alcohol, smoking
What drugs are used in 2nd line treatment of urge incontinence?
Antimuscarinics preventing parasympathetic M3 contraction of detrusor muscle:
Tertiary amines (bladder selective): Tolterodine, Darifenacin
Mixed action antimuscarinic:
Oxybutynin, Popiverine
3rd line:
B3 agonists- activate sympathetics to relax detrusor
Mirabegron
Common side effects of anticholinergics:
Relaxing= let it all hang out
Dry mouth Constipation Blurred vision Urinary retention Cognitive impairment Skin rash with transdermal patches
What are the principles for managing mixed incontinence?
Manage the predominant symptom
If unclear- what occurred first?
What is the difference between low flow and high flow priapism?
What causes it?
Low flow is ischaemic/veno-occlusive priapism where inability of blood to leave penis means a erectile state persists. Pain due to ischaemia.
High flow is due to nonischaemic/arterial inflow into the cavernus spongiosum, more uncommon and painless.
Low flow- haem abnormalities, malignant infiltration.
High flow- arteriovenous malformations.
How does a completely patent urachus present?
May get urine leaking through the belly button in adulthood as it provides a conduit from the bladder towards the umbilicus.
In the fetus, the umbilicus contains the umbilical vein, two arteries and the allantois (transports fetal urine out, forms the fibrous urachal remnant)
How can a patent urachus be shown?
Contrast injection with CT
or ultrasound
Differential of lumps in the groin:
Hernia- inguinal or femoral Enlarged lymph nodes Saphena varix- (dilatation of saphena vein) or femoral aneurysm Cord hydrocele or lipoma Undescended testes Psoas abscess
What signs in groin lumps are indicative of hernias?
Cough impulse presence
Reduce on lying down or with applied pressure
(unless contents of bowel etc are ‘stuck’ in hernia)
In regard to scrotal lumps, what does being able to ‘get above them’ mean and what does it tell us?
Superior edge can be palpated.
Indicates that lumps arise within the scrotum rather than descending from above.
How can an inguinal and femoral hernia be differentiated?
The point when the hernia is reduced indicates origin site.
Femoral hernias- below pubic tubercle
Inguinal hernias- above pubic tubercle
(direct- through abdo wall
indirect- through inguinal ring)
Patient has fever and soft fluctuant, compressible mass in femoral triangle that is painful
What is the diagnosis?
Psoas abscess
contains NAV (lateral to medial)
What is the differential or lumps in the scrotum?
Inguinal hernia Hydrocele, varicocele Epididymal or sebaceous cyst Scrotal skin or testicular tumour TB epididymo-orchitis
What is a hydrocele?
A hydrocele is an abnormal quantity of peritoneal fluid between parietal and visceral layers of the tunica vaginalis (a double layer of peritoneum that descends with the testes).
Tunica vaginalis originates from the processus vaginalis and normally obliterates along it’s length except around the testes.
Features of a scrotal lump suggesting a hydrocele:
Smooth surface, with palpable superior margin
Cannot feel the testes- due to tense fluid collection
Transillumination possible (light shone on one side is visible from other side)
What infection can be a secondary causes of hydrocele
Wuchereria bancrofti cause lymphatic obstruction
When would someone get orchitis without epididymitis?
What sign might be present if so?
Can be due to a viral infection, like mumps where enlargement of salivary/parotid glands may also occur.
Patient has a dull ache in scrotum. On inspection there is a ‘bag of worms’ appearance of the testes.
Varicocele- dilatation of the pampiniform plexus that extend up the spermatic cord.
65 year old man has red scaly plaque on penis that is getting gradually bigger.
What could it be and how is it treated?
Bowen’s disease- squamous skin carcinoma in situ
(could be psoriasis, condylomata- syphilitic warts, balanitis)
IHx: biopsy
Photodynamic therapy, cryotherapy, 5-FU
preferred over excision.
What counts as significant haematuria?
1+ on dipstick
> 3 RBCs on high power field in microscopy
How sensitive is urine cytology for picking up bladder cancers?
30% of low risk bladder cancers
90% of high risk bladder cancers
NMP22 biomarker is expensive but similar sensitivity.
What might the urine dipstick show that indicates haematuria is more likely to be due to a kidney cause rather than a urological/bladder cause?
The presence of protein, which arises from casts suggests kidney cause is more likely.
What can cause proteinuria?
Physiological/strenuous exercise Renal disease- glomerular, tubular-interstitial, renal vascular Multiple myeloma (Ig light chains)
What can cause a false negative in urine dipsticks for white blood cells?
Concentrated urine
Glycosuria
Presence of urobiligen
Consumption of much ascorbic acid (vit C)
What type of bacteria convert nitrates to nitrites, which may be detected with urine dipstick?
Gram negative
Red blood cells will appear dysmorphic on urine microscopy if they have arisen from bleeding in which part of the kidney/bladder?
The glomerulus of the kidney
during their passage they become distorted, may form casts.
Hyaline casts containing just mucoproteins (not WBCs or RBCs) could be due to what?
From tubular epithelial cells: Exercise Heat exposure Pyelonephritis Chronic kidney disease
In urine microscopy, casts with RBCs in them suggest what?
Glomerular bleeding
In urine microscopy what difference might you see in the casts in acute glomerulonephritis or tubulointerstitial nephritis compared to chronic renal disease?
CKD- hyaline casts (mucoproteins of tubular epithelial cells, no RBCs)
Glomerulonephritis- white blood cells in casts too.
What is cystinuria and what is it’s inheritance?
A genetic cause of kidney stones
Autosomal recessive
What’s the difference between cystinuria and cystinosis?
Cystinuria = failure to renally reabsorb cystine Cystinosis = intracellular cystine accumulation leading to Fanconi syndrome due to failure to transport it out of cellular lysosomes
(Cystine is a homodimer of amino acid cysteine)
Staghorn calculi may be composed of which minerals, when do they tend to arise?
Struvite- magnesium ammonium phosphate
Calcium carbonate
Cystine stones
Tend to arise with infections from organisms capable of splitting urea (proteus, pseudomonas, klebsiella).
How can suspected cystinuria be investigated?
Stone analysis
Urine analysis- cystine crystals
Cyanide-nitroprusside test of urine (if positive 24hour urine collection and cystine level)
Which type of renal stones precipitate in acidic urine?
3 C’s
Calcium oxalate (CaC2O4)
UriC acid
Cystine
Which renal stones precipitate in alkaline urine?
2 P’s
Calcium phosphate Triple phosphate (struvite)
What can be the cause of a positive urine cytology result?
Urothelial malignancy
Radiotherapy/chemotherapy in the last 12 months
Urinary tract stones
What is the commonest type of kidney stone?
Calcium oxalate (precipitates in acidic urine)
What are the top five causes of kidney stones, which are radiolucent?
75% Calcium oxalate (opaque- acidic) 15% Struvite (often opaque- alkaline) 5% Calcium phosphate (opaque- alkaline) 5% Uric acid (Lucent- acidic) 1% Cystine (Lucent- acidic)
Which kidney stones are radio-lucent?
Those without calcium in them: Uric acid Cystine Struvite Xanthine
Anti-retro viral drug stones (can’t see on CT)
Pure matrix stones
Which kidney stones are radio-opaque
Those with calcium in them:
Calcium oxalate
Calcium phosphate
Sometimes:
Struvite (triple phosphate)
Patient taking HIV treatment experiences intense colicky loin pain.
CT and Xray are unremarkable.
What could be the cause?
Indinavir-induced renal stone
Which opacities can be confused with stones on Xrays?
Calcified lymph nodes
Or pelvic phleboliths (calcified vein)
For a pregnant woman with suspected renal stones, what imagine modality may be best?
MRI
CT and Xray expose woman to radiation
However rarely are stones confidently excluded or diagnosed with MRI
What can cause post-void residual urine?
Detrusor underactivity- lack of sustained contraction with ageing or neurological disease
Bladder outlet obstruction
What is the key thing residual urinary volume post-void can tell urologists?
Likelihood of back pressure on the kidneys, thus whether it is safe to watch and wait rather than transurethral resection of prostate
How does citrate prevent kidney stone formation?
It forms a soluble complex with calcium, preventing it from crystallising with oxalate or phosphate.
Citrate and magnesium also prevent aggregation of crystals
Patient is found to have hypercalcaemia and a kidney stone. Which other abnormality are they likely to have?
Primary hyperparathyroidism.
PTH = increased Ca2+, decreased PO4-
Which three things cause low levels of urine citrate and predispose to stone formation?
Things that cause proximal tubule to be acidotic increase citrate reabsorption in proximal segment by sodium-citrate cotransporter.
(Cotransporter needs citrate in a 2- ion form.
Citrate 3- ion + proton = citrate 2- ion for uptake)
- Distal renal tubular acidosis (inability to secrete H+ into tubule causes acidosis)
- Hypokalaemia (low K+ may means more H+ swapped for Na+ in proximal tubule)
- Carbonic anhydrase inhibitors
Why does uric acid form in acidic urine?
Uric acid > Sodium urate + H+
The more H+, the more the reaction goes backwards.
Uric acid is insoluble, sodium urate is soluble.
Which type of renal stone is associated with gout?
Uric acid
What is the pathophysiology of type 1 renal tubular acidosis?
What metabolic features do patients get?
Distal RTA:
Insufficient secretion of H+ in the distal portion
Urine becomes alkaline.
Metabolic acidosis
Hypokalaemia (swapping more K+ for Na+)
Low urinary citrate (acidosis in proximal tubule due to more H+ in blood = more citrate 3- converted to citrate 2- for transporter uptake)
Hypercalcaemia (as bone releases CaPO4 to buffer acid)
What causes Type 1 Renal Tubular Acidosis?
Autoimmune diseases- Sjogrens
Inherited
What is the pathophysiology of type 2 renal tubular acidosis?
Proximal RTA:
Failure to resorb bicarbonate in the proximal tubule
More bicarbonate in tubule uses up H+ ions that are needed to turn citrate 3- to citrate 2- so it can be reabsorbed.
Therefore tubular alkalosis leads to increased citrate excretion
Which type of renal tubular acidosis puts the patient at greater risk of stone formation?
Type 1 distal RTA, acidic proximal tubule leads to more citrate uptake and lower levels in urine.
In Type 2, more bicarbonate in tubular (lack of reabsorption) leads to less protons to convert citrate 3- to citrate 2-, so less citrate reabsorption means high citrate urine levels, preventing calcium oxalate crystallisation.
Why do struvite kidney stones form?
Urease-producing bacteria (proteus, klebsiella, pseudomonas) break down urea into ammonia and alkinates urine. In alkaline conditions, magnesium, phosphate and ammonium precipitate.
